The entire disclosure of Japanese Patent Application No. 2006-256201, filed Sep. 21, 2006 is expressly incorporated herein by reference.
1. Technical Field
The present invention relates to actuator devices for liquid ejecting heads. More specifically, the present invention relates to an actuator device comprising a piezoelectric element, which is configured to include a lower electrode, a piezoelectric layer made of a piezoelectric material, and an upper electrode formed on a vibrating plate.
2. Related Art
Typically, an actuator device of a liquid ejecting head includes a piezoelectric element comprising a piezoelectric layer formed of a piezoelectric material with an electromechanical conversion function, such as a crystallized piezoelectric ceramic. The piezoelectric layer is interposed between two electrodes, a lower electrode and an upper electrode. Such actuator devices are generally called flexural vibration mode actuator devices and are mounted in liquid ejecting heads. An example of a liquid ejecting head is an ink jet recording head wherein a portion of a pressure generating chamber communicates with a nozzle opening for ejecting ink droplets. The ink jet recording head is formed using a vibrating plate which is vibrates in response to a piezoelectric element in order to apply pressure to ink in the pressure generating chamber and thereby discharge ink droplets through the nozzle opening. Generally, the piezoelectric element is manufactured by forming a piezoelectric layer and an upper electrode layer on the surface of a substrate provided with a lower electrode. The layers are created using a film formation technique and then using lithography to cut the piezoelectric layer and the upper electrode layer into shapes which correspond to the pressure generating chambers so as to form a plurality of independent pressure generating chambers.
One difficulty in the current configuration of the actuator device, however, is that since the actuator device is repeatedly driven in the ink recording process, there lower electrode layer may peel off from the its base. In order to solve this problem, Japanese Patent Application No. JP-A-2005-176433 discloses an actuator with improved adhesion between the insulating layer and a lower electrode, created by improving the crystallinity of the insulating layer. In one example, the insulating layer includes a crystal plane of zirconium oxide (ZrO2) oriented in the (−111) direction.
However, in order to improve the durability and reliability of the actuator device, the adhesion between the layers much be further improved.